Regional Planning Commission Big Cedar Lake Watershed Land Use and - - PowerPoint PPT Presentation

‹#›

Southeastern Wisconsin

Regional Planning Commission

Big Cedar Lake Watershed Land Use and Pollutant Loading Update

June 22nd, 2020

‹#›

Background and Goals

➢Most recent plan for Big Cedar Lake is MR 137

• Published in 2001; uses 1995 land use data

➢Many conservation practices have been implemented since

• Land easements and conservation
• Stormwater management practices
• Nonpoint source best management practices (BMPs)

➢Goals:

• Update land use and pollutant loading information
• Evaluate changes since 1995
• Identify opportunities to enhance water quality protection efforts

‹#›

1995 Watershed and Subbasins

➢Watershed is an area that contributes surface water runoff to a waterbody

• Includes the waterbody itself
• Boundaries determined by topography and hydrology
• Groundwater is not generally considered in watershed

delineation

➢1995 watershed area total was 6,641 acres

• Included 932 acres for Big Cedar Lake
• Contributing watershed was 5,701 acres

▪ Split into 20 subbasins

‹#›

1995 Land Use

➢Agricultural and open land uses predominant

• 3,056 acres (53% of contributing watershed)

➢Surface waters, wetland, and woodland common

• 1,428 acres (25% of contributing watershed)

▪ Includes 44-acre Gilbert Lake and 12-acre Mueller Lake

➢Urban land use is largely residential

• 746 acres of residential (13% of contributing watershed)
• 476 acres of all other urban land uses combined

‹#›

1995 Pollutant Loading

➢Different land uses contribute different types of pollutants

• Rural uses generally contribute more phosphorus and sediment

▪ Can cause nutrient enrichment problems

• Urban uses generally contribute more metals (e.g., cadmium, copper, zinc)

▪ Metals are toxic for humans and aquatic organisms above recommended levels

➢ Used land use data with pollutant models to estimate pollutant loads

• 1995 land use used for pollutant loading in MR 137

➢2,340 pounds of phosphorus and 670 tons of sediment loading per year to Lake

• Primarily from rural land uses

➢Metals loading determined to pose little threat to Big Cedar Lake

‹#›

Changes in Land Use Mapping and Classification

➢Changes that affect comparison between 1995 and 2020

• Land use digitized in 2000 to match real property boundaries
• Wisconsin Wetland Inventory in 2005 (WWI)
• Reclassification of land use categories

➢Difficult to distinguish changes in actual land use versus classification

• Lake surface area and subbasin boundaries changed with digitization
• Wetland acreages increased due to more accurate mapping
• Roadside and open lands more explicitly mapped and classified

➢Important to consider these effects for 1995 and 2020 comparison

‹#›

2020 Land Use

➢Agricultural and open land uses still dominant, but fewer cultivated acres

• 43% of contributing watershed
• Open lands increased by 32%

▪ Land in conservation easements ▪ Conservation Reserve Program (CRP)

➢30% increase in residential land use

• Little change in other urban uses

➢Slight increase in wetlands and woodlands

• Partially an artifact of WWI
• May also reflect conservation efforts

‹#›

2020 Pollutant Loading

➢Modeled nonpoint source pollutant loads

• Phosphorus and sediment
• Metals (cadmium, copper, and zinc)

➢Subbasin 15 has highest total phosphorus and sediment loads

• 1, 2, 11, 12, and 15 have highest loads per acre

➢Decrease in pollutant loading since 1995

• Shift to less intensive rural land uses

▪ 14% decrease in phosphorus ▪ 20% decrease in sediment

• Slight decrease in metals

▪ Likely mostly due to changes in mapping

‹#›

Watershed and Subbasin Boundary Revisions

➢Watershed delineation updated to more accurately reflect current hydrology ➢Subbasin 1

• Delineated internally draining areas north of STH 33

▪ Do not contribute surface water to Lake

➢Subbasin 13

▪ Removed area that contributes to East Branch Rock River

➢Subbasin 19

▪ Former internally draining area now contributes to Lake ▪ Removed area that contributes to Washington Creek

‹#›

Land Use and Pollutant Loading with Revisions

➢Revisions decreased watershed by 368 acres

• 26 internally draining acres
• Only Subbasins 1, 13, and 19 affected

➢Mixture of land uses in removed areas

• Agricultural, recreational, wetland, and woodland

➢Further decreased watershed pollutant loads

• 80 fewer pounds of phosphorus
• 14 fewer tons of sediment
• Slight decreases in metals loading

‹#›

Nonpoint Source Load Reduction Goals

➢Big Cedar Lake watershed part of 2018 Milwaukee River TMDL

• Impairments include degraded habitat, excessive algae, poor water clarity
• Phosphorus and suspended solids (sediment) are identified pollutants
• Watershed discharges into impaired Cedar Creek

➢TMDL sets watershed pollutant reduction goals for Cedar Creek (MI-18):

Pollutant Nonpoint Source Pollution Sources Non-permitted Urban Sources MS4 Systems Total Phosphorus 40% 69% 68% Total Suspended Solids 63% 72% 71%

‹#›

Ongoing Efforts to Reduce Nonpoint Source Loads

➢Many active organizations implementing conservation practices within the watershed

• Big Cedar Lake Protection and Rehabilitation District
• Big Cedar Lake Property Owners Association
• Cedar Creek Farmers
• Cedar Lakes Conservation Foundation
• Town of West Bend
• Washington County

➢Constructed stormwater basins, drainage channels, and other BMPs to mitigate pollutant loads ➢Increased acreage of lands in easements and CRP

‹#›

Opportunities to Reduce Loads in Urban Areas

➢Meet or exceed MS4 permit requirements

• Improve existing BMPs and develop informational workshops

➢Enhance stormwater management infrastructure

• Direct runoff into vegetated buffers and swales

▪ Install ditch turnouts and ditch checks

• Require green infrastructure/low impact development

➢Reduce pollutants from residential areas

• Enhance shoreline and riparian vegetation buffers

▪ Funding through WDNR programs

• Direct roof and driveway runoff into rain gardens
• Avoid pollutant spills and excessive use

‹#›

Opportunities to Reduce Loads in Rural Areas

➢Support and collaborate with producer-led groups

• Recruit to install low-cost BMPs
• Provide education and outreach opportunities
• Offer financial support to purchase key equipment for

agricultural BMPs ▪ Cover crops, no-till, buffers

➢Sponsor grant applications

• Surface Water Grants Program (now NR 193)
• Targeted Runoff Management Grant Program
• Urban Nonpoint Source and Storm Water Management

Grant Program